Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

If they are, your system isn't stable. If all the stars were the same luminosity/mass, the heating and gravity from each star would vary exactly the same way, and a planet getting more heat from a second star is also more strongly attracted to that second star, and thus isn't orbiting the first. That L/M ratio isn't constant, so it's theoretically possible this could happen, but the perturbations would be so huge every planetary year the orbit couldn't possibly be constant over long periods.

Your stars are still 150 plus AU apart right? Unless your "outermost" orbits are enormous you probably have a math error.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

First of all, free electron lasers aren't actually lasers - they don't have a lasing medium at all so the only heating problems come from the efficiency of your superconductors.

Secondly, heat pumps and radiators. This is again a brute-force approach; you pump the heat out of the FEL and into a high-temperature radiator. A highly conductive surface with a temperature of, say, 2000 Kelvin is going to be losing heat like crazy in space. With current technology you can effectively force-radiate 4 joules for every joule you spend running the heat pump or so. So the only limit to how much heat you can get rid of is the surface of your radiator and how much energy you got available - which is not going to be a problem due to a concentrated-sunlight solar plant providing it.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

I think I said this earlier, I dropped the distances down. The mentioned star is a K2 orbiting a G4 at 51 AU, which in turn orbits and F5 at 136 AU. There's 3 other stars, a G0, G8 and a M0, but their 2000+ AU off. The other 5 stars heat the K2 a total of 94 degress

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Looks like math error to me then. Using the high end of luminosities for those (0.6, 0.8, 2.5, 1.5, 0.5 and 0.08 Lsun, the contributions of the stars other than the K2 at closest approach to the F5 should at the K2 would be 1360 W/m^2 times the sum of
1.5/2000^2
0.5/2000^2
0.08/2000^2
0.8/51^2
1.5/(136-51)^2

Or 0.889 W/m^2. Which is fairly minor. Are you adding temperature contributions instead of energies? By themselves those stars would heat something at the K2 to about 33 K, that is

The Stefan-Bolzmann constant is 5.67 x 10^-8 W/m^2K^4, and a test sphere of 1 m^2 cross section has a surface area of 4 pi, so a blackbody temperature T such that

0.889 W = 5.67 x 10^-8 W/m^2K^4 x pi m^2 T^4

For some other planet, say one at 0.8 AU from the K2 the combination would be about that 0.889 W/m^2 + 1360 x (0.6/0.8^2) = 0.889 + 1275. It should be fairly clear the other sun's contribution is minor. That extra 0.889 W/m^2 raises the blackbody temperature there by 0.006 K. As for equality, the K2 would contribute 0.889 W/m^2 at 30.3 AU, at which point that planet would have a temperature of 40K, and would sometimes be closer to the G4 than the K2 and thus not stably orbiting the K2.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

So let me see if I got this straight. The OP wants a setting where:

1. It's hard science
2. There's regular cargo shipment between very distant worlds
3. That regular travel does not use multi-stage designs
4. Fusion power is not used for spacecraft

The only way I can see this working involves either

1. Not humans, and therefore not limited by human boredom, age, economy, lifestyle, etc.
2. They devote so much of the planetary economy to this endeavor that they effectively pull themselves up a TL or two.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

malloyd, I've been using the 278*( 4th root of L / square root of R) formula, according to that G0 heats the K2 by 43 degrees, which is quite reasonable for something orbiting at 50 AU. The systems age is 3.7 billion years, so the L values of the stars are (Round to two decimal places):
F5: 4.36
G0: 1.58
G4: 0.79
K2: 0.27
G8: 0.46
M0: 0.09

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Sounds like you're adding in the wrong place. For multi-star systems, you need to sum L/R^2 for all stars before taking the 4th root.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Sum L/(R^2) for all stars, then take the 4th root?

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Yes, I assume operator precedence of exponents is higher than division.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

OK, I've done that, net result is to reduce the amount of heating produced by the other stars by about half.

I've just got to figure out if it's possible/worth it to save the other habitable planets, with the older heating values I was getting two orbits inside the life zone

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

SCC, you might consider dropping the TL of one of the more advanced drive systems and/or advancing the TL of the society in that area, so that you can use antimatter rockets or total conversion or whatever you need to get back and forth in a reasonable time. This also makes it cheaper, so that there is a margin for wasteful practices like import bans on crop seeds, and you can introduce the in-continuity reason for them when you come up with one.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

That would require super science, something OP doesn't want.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Actually things are probably within tolerable at the moment. I'm getting $20 per pound shipping.

And anti-matter doesn't work like that. In fact it's not a fuel, you lose too much energy in the annihilation event (Most of it isn't easily usable)

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Unless you have some way of directing all those neutrinos. But even optimal production would take loads more money than any other type of power.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

It's not just neutrinos, it's well, everything. Antimatter annihilation does produce the E=(2)MC^2 energy, but not in a convenient form

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Antimatter-powered neutrino drives aren't necessarily superscience, but they are like TL11 or 12.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

No the no trade possible argument. Unless the colony ships are one-way affairs the ships will be making round trips and it won't be long before someone decides that them coming back empty isn't the best idea

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

But why would the colony ships not be one-way affairs?

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Because it's not cost effective. Then there's the added problems of how you break down the spaceship (Likely still in orbit) and what you do with it once you've broken it down (Most of it's hull is/was metal).

And once the ship is in orbit around the colony planet all it needs is a re-fuel and enough food to see the crew home for it to make a return trip. Given that I'm putting Open Spaces so that I've got total life support, meaning no food or other crew consumables are need, and Magsails, which need no fuel, there's no good reason NOT for them to make round trips

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

...Because the fuel would be massively expensive? Though you seem to have concluded otherwise on the basis of calculations you're keeping to yourself.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Well, Ulzgoroth, given that the ships I've designed need no fuel.

That said, I do have shipping costs now. The price to ship one ton 136 AU is $13,000 while the shipper is still in hock to the banker and $2,500 when the banker's of his back. Orbit and back comes to $10,000. Note that these are cost to shipper values for the most part, the second 136 AU might actually come close to what people pay

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

I've been playing around the numbers some more, and have some updated figures. Mainly by noticing a way to game the system, it's not much, but it helps. Won't stand up in reality, but for a game it's good enough (Cramming 10 fuel tanks into the space of 9 is a physical impossibility)

At worst the fuel to ship a ton into orbit is ~$4,700 per ton, or $2.12 per pound.

Shipping between the two stars cost the company less then $7,000 per ton, or $3.09 while the ships in hock to the bank, or ~$1,100 per ton or $0.51 when the interests paid off.

So it should cost NO MORE then $15 to ship a pound of something between the two stars, at maximum.

For reference I looked up the Australia Post costs to ship stuff, the lowest rate to the US for 500 grams (about a pound) is $10.50, and that's by sea, air freight seems to run to about twice that

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

Note that the $10.50 cost you site is for door to door delivery (or at least Post Office to door), while the $15 cost is for Port to Port delivery, and does not take into account docking fees, loading fees, unloading fees, taxes, tariff, or actual delivery from door to port then from port to door. Nor do you seem to take into account crew costs.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

I just want to check that I've implemented this right

Sum the L/R^2 values for the stars other the planets primary, take the quad root and multiply by 278, then add that to the heating value from the primary, or do I sum the L/R^2 for all stars including the primary, take the quad root and multiply by 278?

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

The latter.

Re: [Space/Spaceships] Getting the velocity/Delta V I want with the tech I want
 

OK, that' reducing the heating effect of the other stars to pretty much nothing, does that sound right?